I'm just getting confused with my comparing my drug release (from nanofibres) data to the mathematical models I have come across. I'm trying numerous things, and coming to dead ends. Here is one of them:

I'm new to drug release modelling, so it's my first time. My wet fibres have surfactant in them. My dry fibres don't have surfactant. My results not only basically show a linear line, but they don't reach the maximum release at 30 minutes, that my data does.

I wanted to model these equation, but I don't know how to get the bessel functions?:

The shorter solutions are here, so I tried using them:

To get a graph like this:

But my graph is like this:

I'd at least like to get the trend going nicely for the wet fibres to hit 90-100% by 30 minutes, and the dry fibres to hit 45% by 30 minutes. It's getting all confusing!

Just to let you know:

1. On Excel, I have the concentration of drug released at each point in time.
2. I have the maximum concentration of drug inside my nanofibres.
3. This is my real data, I wanted to have a curve that was similar to the dotted log lines:

I am using MATLAB, to follow some models, to try and compare my data to models, here is my code:

sum_vec_dry = zeros(1,17);
conc_dry = 0;

sum_vec_wet = zeros(1,17);
conc_wet = 0;

for n = 1:17
    t = 1:1.76:30;

    %dry fibres
    D_dry = 1.2*10^-10; %diffusion coefficient
    radius_dry = (958)/2; %radius of fibre 
    dry_max = 0.27713;

    equation_dry = 1-(4/2.405^2)*exp(-(2.405)^2*D_dry*t(n)/radius_dry^2);

    equation_dry = equation_dry/dry_max;

    conc_dry = conc_dry + equation_dry;
    sum_vec_dry(n) = conc_dry;

    %wet fibres
    D_wet = 10000;
    radius_wet = (789)/2;
    wet_max = 0.0911

    equation_wet = 1-(4/2.405^2)*exp(-(2.405)^2*D_wet*t(n)/radius_wet^2);

    equation_wet = equation_wet/dry_max;

    conc_wet = conc_wet + equation_wet;
    sum_vec_wet(n) = conc_wet;
end


bang_dry = sum_vec_dry;
bang_dry = [0 bang_dry];

bang_wet = sum_vec_wet;
bang_wet = [0 bang_wet];

t = [0 t]
plot(t, bang_dry)
hold on 
plot(t, bang_wet)
hold off
legend('Dry', 'Wet')

ylabel('Percentage of Drug Released (%)')
xlabel('Time (minutes)')
title('Drug Release Mathematical Model')

All help will be much appreciated!! V new to this, and really wanna learn how to model mathematically. There are so many different equations out there, I don't know where to begin... If I could model equation 15, that would be handy, but I don't know how to get the bessel root functions, nor do I know what p means?

REFERENCE is JUERGAN SIEPMANN 2011, Modeling of diffusion controlled drug delivery.